Question 1

Recall that in many plants, if the shoot apical meristem is removed, axillary buds become active and new lateral branches form. What is this an example of?

Accepted Answer

This is an example of apical dominance, where the shoot apical meristem inhibits the growth of axillary buds. When the shoot apical meristem is removed, the inhibition is lifted and the axillary buds become active, leading to the formation of new lateral branches.

Question 2

Fossils show that leaves MOST likely evolved from:

Accepted Answer

Leaves most likely evolved from photosynthetic stems. This evolutionary adaptation allowed plants to increase their surface area for photosynthesis, leading to more efficient energy capture from sunlight.

Question 3

In plants, cell division and increase in size generally occur in different growth zones.

Accepted Answer

In plants, cell division generally occurs in the meristem, while increase in size occurs in the elongation or differentiation zones. These zones are distinct from each other.

Question 4

_____ are cells that lay the framework for new phloem and xylem in vascular plants. Prior to the differentiation of these cells, their precursors transported auxin out of immature leaves.

Accepted Answer

The answer of _____ are cells that lay the framework...

Question 5

A researcher creates a mutant pea plant in which cytokinins are overexpressed and gibberellic acid is underexpressed. What is the MOST likely phenotype of this mutant pea plant?

Accepted Answer

Cytokinins promote cell division and can lead to increased branching, while gibberellic acid promotes stem elongation. Overexpression of cytokinins and underexpression of gibberellic acid would likely result in a shorter plant with more branches.

Question 6

Flower organs:

Accepted Answer

Flower organs, including sepals, petals, stamens, and carpels, are arranged in whorls around the receptacle of the flower. This means that each type of organ is arranged in a circle or ring around the central point of the flower.

Question 7

Plant growth that elongates stems occurs in the:

Accepted Answer

Plant growth that elongates stems occurs in the shoot apical meristem, which is located at the tip of the shoot and produces new cells for stem and leaf growth. The root apical meristem produces new cells for root growth, while shoot lateral and root lateral meristems produce new cells for lateral growth (i.e. growth in width). The internode refers to the region between two nodes on a stem, and elongation of this region is due to stem growth in the shoot apical meristem.

Question 8

Which of the following statements describes the hypothesis proposed to explain the regular arrangement of leaves around the stem?

Accepted Answer

The hypothesis is that auxin accumulation triggers new primordia formation, and existing primordia deplete auxin, leading to new primordia forming at the farthest point from existing ones.

Question 9

Which of the following is NOT a function that can be fulfilled by modified leaves?

Accepted Answer

Modified leaves can fulfill a variety of functions, including protection, attachment for climbing, trapping insects, and insulation. Therefore, none of the answer options are correct.

Question 10

The highly productive varieties of wheat and rice that were developed in the Green Revolution produce lots of seeds. Given that evolutionary fitness is measured in terms of reproductive success (for which total seed production is a good proxy), why might natural selection have failed to produce these highly productive varieties on its own, without the work of human plant breeders?

Accepted Answer

The highly productive varieties of wheat and rice developed in the Green Revolution have reduced stem elongation, which makes them poor competitors for sunlight compared to wild plants. This means they would be outcompeted in natural settings where natural selection would occur. Human plant breeders were able to selectively breed for high yield characteristics without the competition of other plants.

Question 11

A plant has undergone a robust phase of growth; however, the roots can no longer provide enough nutrients to the plant. What signal(s) can the roots send to the rest of the plant that will prevent new branches from forming?

Accepted Answer

Strigolactone is a plant hormone that inhibits branching and stimulates root growth. If the roots are unable to provide enough nutrients, they can signal the rest of the plant to stop branching through the release of strigolactones. This helps the plant conserve energy and focus on growing stronger roots to absorb more nutrients.

Question 12

Cells at shoot tips maintain their totipotency due to the expression of _____ genes.

Accepted Answer

Meristem identity genes are responsible for maintaining the undifferentiated state of cells in the shoot apex, allowing them to retain their ability to differentiate into any type of plant cell. This is what maintains their totipotency. Growth regulation, lateral growth, S-regulation, and nodal expression do not specifically relate to the maintenance of totipotency in shoot tip cells.

Question 13

You are studying a mutant in which cellulose molecules are always deposited in the walls with random orientations, and in which giberellic acid is over-expressed. You find that the:

Accepted Answer

The answer of You are studying a mutant in which...

Question 14

The primary site of photosynthesis in MOST plants is the:

Accepted Answer

Leaves are the primary site of photosynthesis in most plants. They have specialized structures called chloroplasts, which contain chlorophyll and are essential for photosynthesis to occur. Stems, roots, buds, and shoots are not as involved in photosynthesis as the leaves.

Question 15

At the tip of each branch, the _____ surround(s) the shoot apical meristem.

Accepted Answer

Leaf primordia surround the shoot apical meristem at the tip of each branch, forming new leaves.

Question 16

Flowering is triggered by the production of _____, which triggers the transition from apical meristem to floral meristem identity.

Accepted Answer

The production of florigen triggers the transition from apical meristem to floral meristem identity, thus initiating flowering.

Question 17

In seed plants, branches grow out from _____, which are meristems that form at the base of each leaf.

Accepted Answer

Axillary buds are meristems that develop at the base of each leaf and have the potential to form a branch or shoot. Apical buds are found at the tip of the stem, while bud scales are protective coverings for dormant buds. Augmented buds and flower buds are not involved in branch growth in seed plants.

Question 18

Consider the following excerpt of Fig. 31.9 from your text. What phenotypic effects would you expect to observe if a mutation leads to the loss of the plant cell's ability to control where PIN proteins are inserted in the plasma membrane?

Accepted Answer

The answer of Consider the following excerpt of Fig. 31.9...

Question 19

Suppose the pH in the cell walls of an apical meristem became highly basic ( > pH 7), but traffic through PIN proteins in the membrane remained normal. Where would you expect most auxin molecules to be concentrated-in the cell wall or cytoplasm? Would the auxin molecules be in the charged or uncharged form?

Accepted Answer

A high pH in the cell walls would cause the dissociation of auxin molecules from the carboxyl group, resulting in an increase in the charged form of auxin. As a result, most auxin molecules would be concentrated in the cell wall.

Question 20

Flowers may develop from:

Accepted Answer

Flowers can develop either from an apical meristem (terminally) or an axillary bud (laterally). Flowers cannot develop from a leaf meristem, as leaves and flowers are different structures. Lateral meristems, such as the cambium, are responsible for secondary growth in plants and do not produce flowers directly.

Quiz 31: Plant Growth and Development